Purpose:This is a study about a new investigative drug, pembrolizumab (MK-3475) that is being studied in a clinical research trial together with standard chemotherapy (HiDAC) in relapsed and refractory AML. The study will also explore the association between potential immune biomarkers and clinical outcomes with pembrolizumab; therefore all patients will have blood and bone marrow samples collected before and after treatment to determine the dynamic nature of immune signatures pre and post-treatment.